The invention relates, in general, to gun launched grenades, and, in particular, to a new and useful movable and tiltable fuse arrangement which can be used for a number of different projectile sizes and projectile velocities. The invention provides a fuse with a clock-type mechanism to move a detonator from a safe to an armed position which requires the occurrence of two different physical phenomena.
Clock-type mechanisms to move critical elements of the initiation train, i.e. the detonator, from a safe to an armed position are known. Also known are designs which require the occurrence of a minimum of two different physical phenomenon in order to move the clock-type mechanism so that an explosive warhead must move a minimum specified distance away from the gunner to prevent completion of the initiation train prior to the projectile having travelled the minimum specified distance.
The fused design of the M550 is composed of two separate mechanical assemblies which joined together in the nose of the projectile, provide a means whereby a projectile will travel a safe distance before the detonator is moved to an armed position whereby the warhead can be exploded. The first mechanical assembly is an escapement assembly with an eccentrically rotatably mounted rotor having an eccentric center of mass. The center of mass moves from a factory-positioned first location near a rotational axis of the projectile to a second location being spaced from the rotational axis of the projectile. The rotational movement moves a detonator to a detonating position adjacent a firing pin. The rotor is part of an escapement configuration in which the rotational energy of the rotor is absorbed by a pinion and verge arrangement thereby effecting a timed relationship for the movement of the detonator from the unarmed to the armed position. The timed relationship is dependent upon the number of rotations of the projectile.
The second mechanical assembly includes an actuator assembly in which a number of hammers are pivotally arranged on the forward end of the projectile which, upon sudden deceleration of the projectile, pivot about a pivot point and impact on and force a firing pin rearward into the detonator, provided the detonator is in the armed position.
When the high velocity version of basically the same warhead was begun, it was realized that, theoretically, the same fuse system would work in the high velocity warhead. The high velocity barrel twist rate was not changed, therefore the relationship of the spin rate to the projectile travel remained constant. Theoretically, the same fuse arrangement could be used for the higher velocity warhead. However, the increased set-back force from the increased acceleration, caused the heavy actuator to practically crush the escapement. Further, the greatly increased spin rate would tear the hammers off the actuator by centrifugal force.
Thus, it was desired to use the same escapement system, but another means of initiating the detonator had to be found. The warhead was re-designed to eliminate the actuator assembly and a firing pin was arranged fixed at the forward end of the warhead pointing rearwardly. The detonator-rotor component of the escapement was allowed to slide forward thereby driving the detonator into the fixed firing pin.
Unfortunately, it was found that the detonator-rotor component of the escapement would have to be increased in weight. The increased rotor weight necessitated changes in other components of the escapement as well. Today, there are no common items of any significance between the low velocity warhead and the high velocity warhead fuses, except that they operate with the same off-center center of mass rotor concept.
The heavier escapement mechanism for the high velocity projectile utilizes a journal for the rotor having a first end affixed to a forward end of the projectile body. An opposite second end of the rotor journal is fixed to a rearward end of the projectile body. Similarly, the energy-absorbing pinion gear rotates about a journal which is fixed at a first end to the forward end of the projectile body, and is fixed at an opposite end to the rearward end of the projectile body. Upon impact, the rotor and the detonator are allowed to slide along the length of the rotor journal and the pinion journal to engage the detonator with the firing pin.
Also disadvantageous is that the high velocity fuse configuration proved to be too bulky and inoperative when used in the low velocity warhead.